1. Field of the Invention
This invention relates generally to a monitor designed to aid in the instruction of electric arc welding, and more particularly to an audio monitor for use in instruction and training in the art of welding with both AC and DC welding equipment.
2. Related Art
Arc welding is widely used in the fabrication and repair of metal structures. In general, the source of heat for melting the weld material is an electric welding arc which is commonly referred to as an arc current flowing in the form of a plasma or gaseous conductor. The welding arc flows between the welding electrode and the work piece. The distance between the electrode and the work piece constitutes the arc length, and it may vary as the electrode is consumed.
The arc voltage or current across a welding arc represents very closely the arc length conditions when other conditions of the arc, such as the character of the weld rod used and the type of metal constituting the work pieced, are kept constant. A welding operator usually attempts to hold an arc of a constant length, the value of which is suitable to his conditions of welding, including the composition of the work piece.
A skillful arc welder learns to recognize the sights and sounds associated with a good weld. The skilled welder therefore controls the arc length by adjustment of the electrodes so as to produce a satisfactory weld for the material of the work piece. However, a student learning the art of arc welding frequently finds it difficult to maintain the proper arc length and to become conditioned to the sights and sounds associated with a satisfactory continuous weld.
Various attempts have been made at providing systems for monitoring arc weld length and to provide a form of feedback to the arc welder. For example, U.S. Pat. No. 4,471,207 to Hawkes shows a system for providing an audible feedback signal relating to output current and voltage to provide a synthesized feedback signal having a voltage proportional pitch and current proportional volume or current proportional warble component to the tone.
U.S. Pat. No. 4,375,026 to Kierney describes a monitor for weld arc voltage, current and travel speed. The Kierney invention includes sensors for measuring arc voltage which measurement is run through signal conditioners and the output is sent to comparators for comparison to a reference. High and low alarm signals are used if the arc voltage, current or travel speed are not maintained within preset limits.
U.S. Pat. No. 3,679,865 to Jesnitzer et al discloses an apparatus for controlling electric welding processes wherein microphones or suitable current or voltage transducers produce a signal bearing in response to the discontinuous deposition of metal from the electrode to the object being welded. This signal is shaped in a pulse shape for use to provide an output, either through a gauge or loudspeaker which it helpful to the welder in providing high quality welds.
While these prior approaches appear to be meritorious, they suffer from being unduly complex for practical use in the instruction in welding. Furthermore, there are practical problems associated with these devices for use with both AC or DC welders and in the isolation of the monitoring circuitry from the welding current or voltage.